Among rotary electric machines, attention is being given to a rotary electric machine that includes an interior permanent magnet rotor, in which a magnet is embedded, and achieves high torque at high efficiency. In the following description, the interior permanent magnet rotor will be referred to as an IPM rotor, as IPM stands for Interior Permanent Magnet. The IPM rotor may sometimes be equipped with a sensor magnet for use to detect rotational position of the rotor in addition to a main magnet for rotation.
Patent Literature 1 discloses a technique whereby a sensor magnet is held between two bosses and fixed to a rotor shaft on which the sensor magnet is mounted. Also, Patent Literature 2 discloses a technique for mounting a mounting portion D-shaped in cross section and provided with an elastic piece to a sensor magnet and mounting the sensor magnet to a rotor shaft provided with a mounting portion D-shaped in cross section. The sensor magnet is fixed by a restoring force generated on the elastic piece attached to the mounting portion of the sensor magnet.